1. Field of the Invention
The present invention relates to an information recording medium and a production process thereof.
2. Related Background Art
At present, magnetic recording cards such as credit cards and bank cards have spread as personal information recording media. In recent years, IC cards, optical cards and the like have been proposed as portable information recording media having a greater storage capacity. It is also considered that such cards are applied to electronic moneys, bankbooks in which account data are recorded, and the like by making good use of such a great storage capacity. Although a passport, driver's license or the like has been used as a certifying means for an individual, it has been proposed to use, for example, optical cards and IC cards for these licenses. In order to use the IC cards, optical cards and the like as ID cards, devices for reproducing the information stored in the IC cards and optical cards are newly required. It takes a long time to spread these devices for reproducing the information stored in the IC cards and optical cards to the termini with the spread of the IC cards and optical cards. In the course of their combined use with the conventional systems, it is accordingly preferable to apply visible information such as a portrait, ID number or name to such a card.
The application of character information and image information such as a photograph (hereinafter referred to as "visible information"), which can be usually visually read out by persons, to the card can be conducted by, for example, thermal transfer printers (sublimate type thermal transfer printer, melt transfer type thermal transfer printer, etc.). Such a card is so designed that part of pigments and dyes which form these images and characters formed on the surface of the card diffuse into or mix with a resin forming the surface of the plastic card, thereby enhancing the wear resistance and adhesion strength of the printed characters and images.
By the way, the portable information recording medium dealing with such important information is required to have a construction difficult to forge for the purpose of avoiding the possibility of being illegally used by another third party than the regular cardholder as much as possible. As such methods, there have been proposed, for example, a method in which data of an issuer and/or a particular mark is provided as hologram information on the medium in advance, and a method in which semi-shielding information which cannot be understood only at sight, such as a watermark or microline, is provided. However, when such a card is used as an identification card using only the visible personal information provided on the surface without reproducing the optically stored information, it is possible to impersonate the regular cardholder if only the visible information can be forged. The easiest forging method supposable herein is a method in which the personal information of the regular cardholder provided on the surface of, for example, an information recording medium found is removed, and the personal information of a third party is newly printed. Specific examples thereof include a method in which the printed information is removed by dissolution with a solvent, or the printed information and its traces are removed by gradually abrading with finely particulate abrasives or the like, and forged information is reformed by printing such as thermal transfer printing.
There is thus a demand for development of an information recording medium which can more effectively prevent such forgery.